Brief description will be given of a Third Generation Partnership Project Long Term Evolution (3GPP LTE) and LTE-Advanced (LTE-A) as one example of a mobile communication system to which the present description is applicable.
At least one cell exists in one base station. The cell sets one carrier to one of bandwidths, such as 1.25, 2.5, 5, 10, 15, 20 MHz and the like, so as to provide downlink and uplink transport services to several User Equipments (UEs). Here, different cells may be set to provide different bandwidths. The base station controls data transmission and reception for a plurality of UEs. For downlink data, the base station transmits downlink scheduling information to a corresponding UE so as to notify time and frequency domains to which data is to be transmitted, and information related to encoding, data size, Hybrid Automatic Repeat request (HARQ), and the like. Also, for uplink data, the base station transmits uplink scheduling information to the corresponding UE to notify time and frequency domains which can be used by the corresponding UE, and information related to encoding, data size, HARQ and the like. An interface for transmission of user traffic or control traffic may be used between the base stations.
Although the wireless communication technology developed based on Wideband Code Division Multiple Access (WCDMA) has been evolved into LTE, requirements and expectation of users and providers have continued to increase. Also, since another wireless access technology is being developed. new technical evolutions are required for competitiveness in the future. In this respect, reduction of cost per bit, increase of service availability, flexible use of frequency bands, simplified structure, open type interface, proper power consumption of a UE and the like, are needed.
In recent time, standardization of the advanced technology of LTE is in progress under the 3GPP. The technology is referred to as ‘LTE-A’ in this specification. One of important differences between the LTE system and the LTE-A system is difference in system bandwidth and an introduction of a relay.
The LTE-A system aims at supporting a wideband to extend up to 100 MHz. To this end, the system uses a carrier aggregation or bandwidth aggregation that achieves a wideband using a plurality of frequency blocks. The carrier aggregation uses a plurality of frequency blocks as one great logical frequency band in order to use a wider frequency band.
A bandwidth of each frequency block may be defined based on a bandwidth of a system block used in the LTE system. Each frequency block is transmitted using a Component Carrier (CC).